Hadron Therapy

Why hadron therapy for cancer treatment? What is the advantage?

Hadron therapy is not a replacement for conventional radiotherapy or surgery, but is an additional tool that physicists offer of the oncologists. The clinical interest in hadron therapy resides in the fact that it delivers precision treatment of tumors, exploiting the characteristic shape of energy deposition in the tissues for hadrons, i.e. the dose deposition as a function of the depth of matter traversed. While X-rays lose energy slowly and mainly exponentially as they penetrate tissues, hadrons deposit almost all of their energy in a sharp peak – the Bragg peak – at the very end of their path. Hence hadron beams produce a greater dose to the tumor than to the healthy tissue previously traversed.

The Bragg peak makes it possible to target a well defined cancerous region at a depth in the body that can be tuned by adjusting the energy of the incident particle beam. The dose deposition is so sharp that new techniques are being developed to treat the whole cancerous target; thin pencil-like hadron beam are guided according to the shape of the zone to be treated and cover the target volume in 3D, under the control of sweeping magnets coupled to energy variations. With this technique the tumor can be delineated in all its contours with a precision of 2-3 mm.

When hadron therapy is most convenient to use?

Hadron therapy is mostly used for treating tumors that are located close to vital organs that would be unacceptably damaged by X-rays, or in pediatric oncology, where quality of life and late side effects are a major concern.

Proton, Carbon or other hadrons?

While the advantages of protons over X-rays are quantitative in terms of the amount and distribution of the delivered dose, several studies show evidence that carbon ions damage cancer cells in a way that the cells cannot repair themselves. Carbon therapy may be the optimal choice to tackle radio-resistant tumours but also other light ions, such as helium, are investigated.

Clinical experience in the Japanese centres, uncontested leaders in treatment and clinical studies with carbon ions, has not only demonstrated that carbon therapy is more effective than conventional photon radiotherapy on certain types of tumours but also that, with respect to both protons and photons, a significant reduction of the overall treatment time and the number of irradiation sessions can be achieved.